Fasting is a form of Islamic worship to approach God. There is a direct relationship between fasting, abstaining from eating and drinking, and an individual’s health as well as his ill-health. Therefore, it is of utmost importance in the Islamic perspective to weigh the spiritual benefits achieved through fasting against its probable harmfulness to an individual’s health. Regarding fasting, the Islamic perspective is based on spiritual and social goals whose achievement centers around fasting according to the Islamic principles. But, in medicine, fasting is merely dealt with abstaining from eating and drinking which is regarded as one aspect of this Islamic ritual. Additionally, the concept of harmfulness is defined as making a defect or disorder occurring in the body, the recognition of which is within the responsibility of medicine and the decision about which is within the responsibility of an individual. Medical science can determine the effects and consequences of thirst and hunger during the month of Ramadan. In the religious perspective, it has been emphasized that fasting is for achieving the divine virtue, and this shouldn’t be in conflict with maintaining man’s health. Therefore, the conditions in which there is the probability of harmfulness to man’s health due to fasting, man shouldn’t fast. As a result, medical science could recognize the conditions in which there is probable harmfulness to man’s health.